Field of the Invention
The field of the invention is cleaning apparatus for cleaning carriers used to hold and process semiconductor wafers, substrates, flat panel displays and similar flat articles requiring low contamination levels.
The processing of semiconductor wafers, substrates, photomasks, flat panel displays, data disks, optical media and other articles relating to the semiconductor industry (collectively referred to here as xe2x80x9cwafersxe2x80x9d) is very sensitive to problems of contamination. These articles require extremely low contamination levels. Even tiny contaminants can cause defects. Accordingly, it is necessary to maintain a high level of cleanliness during virtually all stages of manufacture.
Semiconductor wafers are typically processed in batches. Batch handling may occur throughout the entire production process, or for one or more processing steps or related handling operations. Batch processing almost always uses some type of carrier to hold the wafers. The wafer carriers can be of various designs. Carriers in the form of a protective case or box are often used. In these types of carriers, the wafers are held and enclosed against contamination during travel within the processing facility. The wafer carriers must be cleaned, to avoid having particles and contaminants on the carriers contaminate the wafers. However, cleaning wafer carrying boxes can be difficult because they typically have features such as slots, grooves or apertures.
One type of wafer carrier is known as the front opening unified pod, or FOUP. A FOUP carrier has a five-sided box with an open front. A door attaches to the front of the box, to seal the box against entry of external contaminants, to help keep the wafers clean. The door has a latch mechanism, which is typically adapted to be engaged and operated automatically via robots or other automatic machinery. The latch mechanism is largely contained within hollow spaces within the door. The hollow spaces within the door, and other interior door features, make cleaning the FOUP door difficult, using conventional techniques. The hollow areas trap water or other cleaning fluids. Accordingly, improved apparatus and techniques are needed for cleaning FOUP doors.
Box carriers have been successfully cleaned in centrifugal cleaners. See, for example, U.S. Pat. No. 5,738,128, incorporated herein by reference. In these centrifugal cleaners, the box is loaded onto a rotor, with the open top or front side of the box facing radially outwardly from the rotor. The box is then sprayed with cleaning fluids, and then with drying gases, while the rotor turns. Centrifugal force helps to remove cleaning fluids from the box, to help dry it. While these techniques have worked well for different types of boxes, FOUP carriers have larger five-sided boxes. Accordingly, FOUP boxes cannot be readily loaded onto, or securely held in place on, a conventional rotor in a centrifugal box cleaner. Accordingly, an improved centrifugal box cleaner is needed for use with FOUP boxes.
As FOUP carriers include a box and a separate door, which must both be cleaned, a system for efficiently cleaning both of these components of a FOUP container is also needed.
In a first aspect of the invention, an apparatus for cleaning a door of a wafer carrier includes an ultrasonic transducer within a cleaning tank. An elevator supports a base adapted to hold several doors, with the elevator lifting the doors into and out of the cleaning tank. A tank lid is advantageously attached to the elevator, and seals the tank, when the base is lowered into the tank. The doors are effectively cleaned, notwithstanding their hollow spaces and other difficult-to-clean features.
In a second and separate aspect of the invention, a centrifugal cleaner for cleaning carrier boxes has a rotor within an enclosure. A box holder on the rotor includes upper and lower hooks. An upper front edge of the box is placed behind the upper hooks. The box is rotated into position, and secured on the rotor by the upper and lower hooks. Accordingly, the box is installed and secured onto the rotor without the need for moving latches or other securing components.
In a third and separate aspect of the invention, a system for cleaning carriers used for handling semiconductor wafers includes a box cleaner having a rotor within an enclosure. Box holder assemblies on the rotor include upper and lower hooks for securing boxes to the rotor. A door cleaner is advantageously located adjacent to the box cleaner. The door cleaner has an ultrasonic transducer within a cleaning tank. An elevator moves doors into and out of the cleaning tank. The boxes and doors are efficiently cleaned and handled at a single location.
In a fourth and separate aspect of the invention, a box door holder assembly is provided on the rotor. The box door holder assembly preferably has a plurality of box door holding positions. Each box door holding position advantageously has a door guide and door hooks for holding a door. The box door holder assembly allows both the boxes and their doors to be cleaned with the centrifugal cleaner, avoiding the need for separate cleaning of the doors.
Other and further objects, inventive features, and advantages, will appear hereinafter. The invention resides as well in subcombinations of the features described.